OPTICAL PERFORMANCES

The best optical performances ever seen – Ti 45 Astrograph

Telescopi Italiani has decided to show a full review about the awesome optical performances of our TI 45 Astrograph –Harmer-Wynne Dual Focal Length – reached thanks the design work carried out by the aerospace engineer Leonardo Priami.

MATRIX SPOT DIAGRAM

SPOT DIAGRAM vs FIELDS

TI 45 f/4 (450 mm aperture- 1800 mm focal length):

TI 45 f/4 Spot Diagram vs Fields

TI 45 f/8 (450 mm aperture- 3600 mm focal length):

TI 45 f/8 Spot Diagram vs Fields

SPOT DIAGRAM vs WAVELENGTH

A very important diagram that nobody shows. Only after analyzing these curves we can see that the optic is really diffraction limited for every wavelengths. The black line is the Airy Disc radius, the numbers are the five fields. TI 45 f/4 (450 mm aperture- 1800 mm focal length):

TI 45 f/4 – Spot Diagram vs Wavelength

TI 45 f/8 (450 mm aperture- 3600 mm focal length):

TI 45 f/8 Spot Diagram vs Wavelength

DISTORTION and FIELD CURVATURE

A great result also about field curvature and distortion. Only 0.32% of distortion @ 30 mm off-axis for the f/4 configuration.

TI 45 f/4 (450 mm aperture- 1800 mm focal length):

TI 45 f/4 – Distortion and Field Curvature

TI 45 f/8 (450 mm aperture- 3600 mm focal length):

TI 45 f/8 Distortion and Field Curvature

RELATIVE ILLUMINATION

The Relative Illumination curve is the ratio between the light hitting the focal plane and the total light incoming. After said this, it is clear that we could reach very high relative illumination only reducing the total incoming light (for example reducing the secondary mirror size (!)). With a under-dimensioned secondary mirror we could have higher relative illumination but with a great loss of light (as if the primary mirror was working with a smaller diameter). We decided to optimize the illumination up to 30 mm off-axis with a well dimensioned secondary mirror. To understand this can help to see also the “Unvignetted Ray graph” that shows the complete collected light from the primary mirror. The 30% of lost light is the exact amount intercepted by the secondary mirror cell.